This invention relates to tufting machines and more particularly to a yarn jerker system therefore for controllably applying different degrees of pull-back on the yarns of selective needles.
It is known to provide a yarn jerker system in tufting machines comprising a jerker member moveable in sychronism with the needle bar and cooperating with a fixed jerker member to tension the yarn and set the stitch in the backing when the needles are at the top of their stroke. The fixed yarn jerker member may be adjustable to vary the yarn path length between the yarn feed assembly and the needles to thereby vary the pull-back in accordance with tufting conditions and the yarn in use. For example, the greater the elasticity of the yarn, the greater the pull required for the same effect. One such adjustable system is illustrated in Parsons, U.S. Pat. No. 3,738,293.
It is sometimes desirable to thread the machine so as to tuft simultaneously with more than one type of yarn, i.e., yarns of different elasticity. For example, carpeting comprising a bulk continuous filament nylon and an acrylic or any spun yarn has aesthetic properties which may be desirable. However, since the tensioning and feeding of yarns of different elasticity are dissimilar, undesirable variations in loop levels have been produced in the product. The known yarn jerker systems have not been successful in compensating for these differences in the yarns. Moreover, the known yarn jerker systems are not by themselves capable of producing textured effects on tufting while the machine is threaded with the same yarn.